An air-stable, Zn²⁺-based catalyst for hydrosilylation of alkenes and alkynes

Abstract

Hydrosilylation of C=C double and C≡C triple bonds is one of the most widely used processes in organosilicon chemistry, mostly catalyzed by Pt-based complexes. We report here the synthesis of...

An “On‐Demand”, Selective Dehydrogenative Borylation or Hydroboration of Terminal Alkynes Using Zn2+‐based Catalyst

“…To solve this issue and achieve better catalytic activity i. e. lower working temperature, we decided to use a less sterically encumbered and less electron donating ligand with pyridinyl “arms”, tris(6‐pyridylmethyl) phosphine (TPPh) [11] to synthesize dicationic Zn‐based complex 1 . Thus, similarly to the previously reported 1 a , [10] the reaction of TPPh with ZnCl 2 followed by the abstraction of two Cl − anions by two equiv. of K[B(C 6 F 5 ) 4 ] led to the desired 1 (Scheme 2).…”

“…The catalytic activity of 1 was first tested in hydrosilylation reactions of alkenes and alkynes. As expected, 1 was an active catalyst for the hydrosilylation reaction at lower temperatures (50–70 °C) compared to its predecessor 1 a [10,12] . However, it is worth noting that the improved reactivity of 1 came at the expense of catalyst selectivity.…”

“…As expected, 1 was an active catalyst for the hydrosilylation reaction at lower temperatures (50-70 °C) compared to its predecessor 1 a. [10,12] However, it is worth noting that the improved reactivity of 1 came at the expense of catalyst selectivity. In contrast to our previously reported Zn-based complex (1 a) that was inactive catalyst in hydrosilylation of carbonyls, 1 (0.5 mol%) catalyzed the hydrosilylation reaction of both C=C and C=E (E = O, N) double bonds.…”

“…Recently we reported an air‐stable, di‐cationic zinc complex in tridentate tris(2‐methyl‐6‐pyridylmethyl) phosphine (TmPPh) hemilabile ligand ( 1 a ) (Scheme 2) that was found to be an efficient catalyst for the hydrosilylation of unsaturated C=C double and C≡C triple bonds, and interestingly was inactive in hydrosilylation of C=E (E=O, N) bonds [10] . One of the major drawbacks of this Zn‐based catalyst was the fact that it required high temperatures (120–140 °C) to be active in these hydrosilylation reactions.…”

“…Recently we reported an air-stable, di-cationic zinc complex in tridentate tris(2-methyl-6-pyridylmethyl) phosphine (TmPPh) hemilabile ligand (1 a) (Scheme 2) that was found to be an efficient catalyst for the hydrosilylation of unsaturated C=C double and C�C triple bonds, and interestingly was inactive in hydrosilylation of C=E (E = O, N) bonds. [10] One of the major drawbacks of this Zn-based catalyst was the fact that it required high temperatures (120-140 °C) to be active in these hydrosilylation reactions. Two factors were suspected in causing 1 a to be inactive at lower temperatures: one is the steric hindrance around the Lewis acidic Zn 2 + reactive center, and two, is the strong electron donating effect of the lutidinyl based arms, somewhat quenching the Lewis acidity of Zn center.…”